Device for compensating for pressure drop

ABSTRACT

The invention relates to a device for compensating for pressure drop in a product pipe through which a liquid flows, and a system comprising such a device. The device comprises a collapsible tube portion, which is connectible to the product pipe, and is characterised by a limiting means, which is adapted to counteract stretching of the tube portion in the circumferential direction and which is adapted to allow free collapsing of the tube portion.

This is a 371 filing of International Patent Application No.PCT/SE2003/001295 filed Aug. 20, 2003 and published on Mar. 4, 2004under publication number WO 2004/018345 A and claims priority benefitsfrom Swedish Patent Application No. 0202487-5 filed Aug. 21, 2002.

FIELD OF THE INVENTION

The present invention relates to a device for compensating for pressuredrop in a product pipe through which a liquid flows, and a system forfilling containers comprising such a device. The invention concerns morespecifically such a device comprising a collapsible tube portion whichis connectible to a product pipe.

BACKGROUND ART

A device for compensating for pressure drop in a product pipe throughwhich a liquid flows is used, for instance, in the food industry forfilling containers in a filling machine.

The filling machine is connected to the product pipe and has a fillingstation, at which liquid contents, such as milk or fruit juice, areintroduced into the empty containers. To this end, the filling stationusually comprises a filling pipe which via a filling valve is connectedto the product pipe. For filling a container the filling pipe isinserted into the container, after which the filling valve is opened.When the filling valve is opened, liquid will thus flow through thefilling valve and into the container. When a required volume has beentransferred to the container, the filling valve is closed. The fillingvalve can be, for instance, time- or volume-controlled. Then the filledcontainer can be conveyed to a sealing station, and a new emptycontainer can be conveyed to the filling station.

When a filling valve is opened, a pressure drop arises in the productpipe. This pressure drop may cause more or less serious disturbances.

The pressure drop can propagate to other filling stations which areconnected to the product pipe and thus affect the filling processeswhich are controlled by the filling valves of the respective fillingstations.

Furthermore the pressure drop can affect the filling process controlledby the filling valve in question. More specifically, the pressure dropaffects the rate at which the product flows through the product pipe.

If the filling valve is time-controlled, the pressure drop thusconstitutes an uncertainty with regard to the accuracy with which thecontainer can be filled. The container can either be filled with toosmall or too large an amount of liquid.

If the filling valve is volume-controlled, the pressure drop impliesthat the filling time required for filling the container increases sincethe pressure drop causes a reduction of the flow rate of the product inthe product pipe.

When the valve is closed after filling, a surge may be generated,propagating through the product pipe. This surge can be detrimental tothe filling station and also affect the filling processes at otherfilling stations connected to the product pipe.

To eliminate, or in any case reduce, these disturbances caused by saidpressure drop, a device for compensating for the pressure changes isusually connected to the product pipe.

Such a known device for compensating for pressure drop and pressurechanges is the so-called balancing or level vessel, which is a containerin which the liquid level is regulated by means of a float whichcontrols the supply of liquid. The liquid level is regulated so as toalways be kept within certain limits, independently of the discharge ofliquid from the container. When liquid is discharged from the container,this occurs by gravity, and no pressure drop or surges that canpropagate will arise, either at the beginning or at the end of thedischarge. The construction, however, suffers from the drawback that itis difficult to clean and sterilise, which are important aspects insystems for filling of containers with liquid food contents. Theconstruction is also relatively expensive to manufacture and install.

SE 410,844 discloses a device for compensating for surges in a productpipe through which a liquid flows, which device partly solves theproblems of the above device as regards cleaning and sterilising. Thedevice comprises a first and a second chamber, adjoining each other andbeing separated by means of a flexible wall. The first chamber has aninlet and an outlet to be connected in series to the product pipe. Thesecond chamber is connected by a control means to a compressed airsource. In case of surges in the product pipe, the wall of the firstchamber is stretched in a manner that corresponds to the surge. Thepressure in the second chamber is regulated so as to compensate for thechange in volume of the first chamber. The pressure drop is taken careof by the first chamber being allowed to collapse.

The device according to SE 410,844, however, has a serious drawbacksince it has a most limited service life. The reason for this is therepeated stretching of the wall of the first chamber which is caused bysaid surges. Up to now, it has proved difficult to find a material whichwith an acceptable service life can be subjected to such strain.

U.S. Pat. No. 6,264,069 discloses a device for dampening surges fromliquids. The device consists of an inner and an outer tube, the innertube being connected to, for instance, a filling system for beverages.The device is intended to dampen surges from a pump in the system. Asurge causes the inner tube to expand until it contacts the outer tube,which prevents further expansion.

The device described in U.S. Pat. No. 6,264,069, however, involvesproblems similar to those of the device of SE 410,844, i.e. the repeatedstretching of the inner tube causes it to obtain a short service life.

U.S. Pat. No. 2,838,073 discloses a device which is adapted to dampensurges in a flame thrower. The device of US Pat. No. 2,838,073 consistsof a resilient inner tube of heavy rubber and an outer reinforced tube.When a surge arises, it will expand the inner tube to absorb the forces.The outer tube ensures that this expansion is only allowed to occur to apredetermined extent. Also this device has the problem of a shortservice life since the inner tube is stretched repeatedly.

U.S. Pat. No. 2,875,786 discloses a device for dampening surges fromliquids. The device consists of an inner non-flexible perforated pipe, aflexible tube which is arranged immediately outside the pipe and asecond, non-flexible tube which encloses the flexible tube. When a surgearises in a system, the flexible tube expands and, thus, dampens thesurge. The other tube ensures that said expansion is only allowed totake place to a predetermined extent. Also U.S. Pat. No. 2,875,786 hasproblems similar to those of U.S. Pat. No. 6,264,069 and U.S. Pat. No.2,838,073 since the flexible tube is stretched repeatedly.

JP 3,175,599 discloses a hose for pressurised systems. The hosecomprises an inner layer and an outer layer. A reinforced layer isarranged on the opposing sides of the respective layers. Aplastic-reinforced layer is arranged between the reinforced layers. Theplastic-reinforced layer serves only to allow the hose to expand to apredetermined extent. The hose of JP 3,175,599 is not intended to affectthe pressure of a system, but still obtains a short service life causedby the repeated stretchings.

There is thus a need for a less expensive and easily cleaned devicewhich can compensate for pressure drop in a product pipe and which alsohas a satisfactory service life.

SUMMARY OF THE INVENTION

In consideration of the above, an object of the present invention is toprovide an improved device and an improved system for compensating forpressure drop in a product pipe.

A special object of the invention is to provide a device, and also asystem for filling containers comprising such a device, for compensatingfor pressure drop in a product pipe, said device being relatively cheap,having a satisfactory service life and being easy to clean.

To achieve at least one of these objects and also other objects thatwill appear from the following description, a device and a system areprovided according to the invention, having the features stated in claim1 and claim 11, respectively, preferred embodiments being defined in thedependent claims.

More specifically, according to the present invention a device isprovided for compensating for pressure drop in a product pipe throughwhich a liquid flows, comprising a collapsible tube portion which isconnectible to said product pipe. The device is characterised by alimiting means, which is adapted to counteract stretching of the tubeportion in the circumferential direction and which is adapted to allowfree collapsing of the tube portion.

This results in an improved device for compensating for pressure drop ina product pipe.

Since the device comprises a tube portion which is connectible to theproduct pipe, a device is obtained, which is extremely easy to clean.The device and its tube portion can, more specifically, be cleaned inconnection with the cleaning of the actual product pipe.

Furthermore, the inventive device can be made to exhibit a satisfactoryservice life. By the stretching being counteracted and thus beingessentially prevented, the tube portion will not be subjected torepeated stretching, thereby eliminating the problems associated withsaid stretching, i.e. a reduced service life as a result of the fatigueof the tube portion caused by said stretching.

-   -   The device is also inexpensive to manufacture, to install and to        maintain since the construction is relatively simple and        uncomplicated.

Nevertheless, the device is capable of efficiently taking care ofpressure drop in the product pipe since the limiting means is adapted toallow free collapsing of the collapsible tube portion.

By free collapsing is meant that the tube will be able to unimpededlyassume a collapsed state. Such free collapsing is decisive in order tobe able to efficiently take care of pressure drop without subjecting thetube portion to strain which negatively affects its service life.

According to a preferred embodiment of the inventive device, thelimiting means is integrated into a tube wall of the tube portion. As aresult, a hygienic device is provided, which is easy to install as wellas to keep clean.

The limiting means may comprise a reinforcement integrated into the tubewall. The reinforcement can easily be adjusted so that stretching of thetube portion is counteracted while free collapsing of the tube portionis allowed, thus obtaining a durable tube portion with a satisfactoryservice life.

According to another preferred embodiment, the limiting means isarranged outside the tube portion. This ensures that the limiting meansmay consist of a conventional reinforced tube, such as a fire hose. As aresult, the inventive device can be provided from relatively inexpensivestandard components, only said tube portion needing to be approved forfoods since this is the only portion that will come into contact withthe product.

The limiting means is advantageously inelastic in the circumferentialdirection. This counteracts stretching in the circumferential directionof the tube portion to such an extent that it is completely prevented.

The limiting means can have such a tensile strength as to preventstretching in the circumferential direction of the tube portion at apressure above atmospheric prevailing in the same in the range of 1–10bar.

The limiting means is advantageously flexible so that free collapsing ofthe tube portion is ensured.

According to a further embodiment, the device comprises a casing, inwhich said tube portion and said limiting means are arranged, pressuremeans being arranged to apply a pressure prevailing in the casing, whichis slightly below a normal pressure prevailing in the tube portion inoperation. This ensures collapsing of the tube portion also in case ofpressure drop where the resulting pressure in the tube portion exceedsthe atmospheric pressure.

The pressure means can be a compressed air means, which in an easy andinexpensive way allows application of said pressure in the casing.

The tube portion of the device is preferably flexible and stretchable inorder to achieve said collapsibility.

Moreover, according to the invention a system is provided for fillingcontainers with liquid contents, comprising a product pipe which leadsto at least one filling station with at least one filling valve. Thesystem according to the invention is characterised by a device accordingto any one of the above devices, which is positioned upstream of said atleast one filling station and connected to said product pipe and whichis adapted to compensate for pressure drop in the product pipe.

This results in an improved system for filling, in which the system willbenefit by the above advantages of the device.

According to a preferred embodiment of the inventive system, the tubeportion is essentially linearly extended and arranged at an angle to thehorizontal plane. This ensures that in case of pressure drop the tubeportion collapses in a manner that promotes discharge of the productthrough the same. More specifically, collapsing will take place in theform of a squeezing filling motion which ensures that the product isdischarged through the tube portion in a satisfactory manner.

The tube portion of the device is preferably arranged at an angle in therange 5–90°, more preferably in the range 10–45°, and most preferably inthe range 25–35°.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail by way ofnon-limiting embodiments and with reference to the accompanyingdrawings. Equivalent components in both embodiments have been given thesame reference numerals.

FIG. 1 is a side view of a device according to the invention in anunaffected state.

FIG. 2 is a side view of a device according to the invention in a stateaffected by pressure drop.

FIG. 3 is a side view of a device according to the invention in a stateaffected by surge.

FIG. 4 is a cross-sectional view of an embodiment of the invention.

FIG. 5 is a cross-sectional view of a second embodiment of theinvention.

FIG. 6 is a schematic view of a system according to the invention.

FIGS. 7 a and 7 b are side views of the device in a collapsed, angledstate.

DESCRIPTION OF A PREFERRED EMBODIMENT

According to the present invention, a device for compensating forpressure drop in a product pipe is provided. Such a device is extremelyadvantageous in a system for filling of containers with liquid foodcontents, the contents being supplied through said product pipe.

Subsequently some preferred embodiments of the present invention will bedescribed, components having an equivalent and similar function beingthroughout given the same reference numerals.

FIG. 1 to which reference is made, illustrates a first embodiment of aninventive device 1.

The device 1 comprises as main components a flexible tube portion 2, alimiting means 3 arranged outside the same and a casing 4 which enclosessaid tube portion 2 and said limiting means 3.

The shown embodiment of the inventive device 1 comprises an inlet 5 andan outlet 6 through which the device 1 is connected to a product pipe 7in such a manner that the tube portion 2 of the device 1 forms part ofthe flow path of the product pipe 7. The part of the product pipe 7which extends from the outlet 6 of the device 1 leads to a fillingstation 8 which is schematically shown in the form of a filling valve 9.The filling valve 9 is openable to allow discharge of a product flowingin the product pipe 7, for instance for filling a container 10.

The tube portion 2 is made of a flexible material which is stretchablein the circumferential direction and tends to collapse when applying apressure which is below the ambient pressure in the tube portion 2. Thedevice 1 is, as mentioned above, connectible to the product pipe 7 andcomprises to this end said inlet 5 and outlet 6, by means of which thetube portion 2 of the device 1 can be connected to the product pipe 7and be made to form part of the same.

The limiting means 3 arranged outside the tube portion 2 surrounds thetube portion 2 in the radial direction and is adapted to counteractstretching of the tube 2 in the circumferential direction.

In the embodiment illustrated, the limiting means 3 is made in the formof a tube 12 of, for instance, fire hose type, which is woven fromnon-elastic threads, schematically shown at 11, said tube 12 beingslipped over said tube portion 2 and thus effectively counteractingcircumferential stretching thereof. This is illustrated more clearly inFIG. 4, to which reference is now also made.

The limiting means 3 can also be designed, for instance, so as toprevent stretching of the tube portion 2 in the circumferentialdirection when applying a pressure prevailing in the tube portion 2,which exceeds the ambient pressure by up to 10–20 bar.

It is important for the limiting means 3 to be such as to allow freecollapsing of the tube portion 2. In other words, the limiting means 3must be such as to not prevent collapsing of the tube portion 2. Inorder to ensure the function of the inventive device 1, which will bedescribed in detail below, it is in fact most important for the tubeportion 2 to be allowed to unimpededly assume a collapsed state.

It is thus not possible to make the limiting means 3 in the form of arigid cylinder which is arranged in a tight-fitting manner on theoutside of the tube portion 2. When the tube portion 2 collapses, itscross-section will in fact be changed so as to be compressed in onedirection and stretched out in another, seen in a plane perpendicular tothe longitudinal direction of the tube portion 2. If the limiting means3 is made of a rigid cylinder arranged on the outside in a tight-fittingmanner, this stretching out of the cross-section is prevented.

Consequently the limiting means 3 must be flexible so that it cancollapse together with the tube portion 2 and thus allow this tounimpededly assume its collapsed state.

It will be appreciated that the limiting means 3 can be provided inother ways. For instance, it is possible to integrate the limiting means3 into the tube portion 2, which is illustrated in FIG. 5. Morespecifically, the limiting means 3 is made of a reinforcement 13 in thetube portion 2, said reinforcement 13 comprising non-elastic threads 11integrated into the wall 14 of the tube portion 2, said threads 11 beingoriented so as to counteract stretching of the tube portion 2 in thecircumferential direction.

As is also evident from FIG. 1, to which reference is made once more,the device 1 comprises a compressed air means 15, which is adapted toaffect the pressure prevailing in the casing 4. The pressure in thecasing 4 affects the outside of the tube portion 2 and the limitingmeans 3 and can be varied according to the current normal pressure inthe product pipe 7. The compressed air means 15 thus regulates thepressure in the casing 4 and is controlled by a sensor 16 which isarranged upstream of the device 1 and senses the pressure in the productpipe 7.

The casing 4 of the device 1 has openings 17, 18 through which the inletand outlet 5, 6 of the tube portion 2 extend to allow connection of thedevice 1, more specifically its tube portion 2, to the product pipe 7.

The function of the device 1 illustrated in FIG. 1 will now be describedwith reference to FIG. 2.

When the filling valve 9 is opened, for instance for filling a container10, a pressure drop arises, which propagates through the product pipe 7.In response to the pressure drop, the tube portion 2 collapses, which isshown in FIG. 2. As described above, the limiting means 3 is arranged insuch a manner that the tube portion 2 is allowed to collapse freely. Thepressure drop caused by the opening of the filling valve 9 will thus becompensated for owing to the collapsing of the tube portion 2, the tubeportion 2, while collapsing, changing its internal volume in a mannercorresponding to the pressure drop. This ensures that the pressure inthe product pipe 7 remains essentially unchanged, thereby achieving therequired accuracy for discharging the product through the filling valve9.

The tube portion 2 is allowed to collapse freely so that, in itscompletely collapsed state, it assumes a flat shape. When the tubeportion 2 is allowed to collapse in this way, no harmful folds arise,which could be detrimental to the service life of the tube portion 2.

When the filling valve 9 is closed, for instance when a container 10 hasbeen filled to the required extent, a surge arises. The surge isabsorbed, i.e. dampened, at least partly by the tube 2 once it assumesits original, non-collapsed state and its volume increases once more, asshown in FIG. 1.

The limiting means 3 can be adapted to allow a small degree of expansionin the radial direction, implying that the tube portion 2 is onlyallowed to stretch slightly, such as by a few percent, in thecircumferential direction, which is illustrated in FIG. 3. This resultsin additional dampening of the surge caused by the closing of thefilling valve 9. However, it is essential for this stretching in thecircumferential direction to be kept small so as to guarantee thenecessary service life of the tube portion 2. By small stretching ismeant stretching which is less than 5% in the circumferential direction.

FIG. 6 shows a preferred embodiment of an inventive system 19 forfilling of containers 10. The system 19 comprises an inventive device 1in accordance with what has been described with reference to, interalia, FIG. 1.

The main components of the shown embodiment of the system 19 is aproduct tank 20, a product pipe 7 connected to the product tank 20, aninventive device 1 connected in series to the product pipe 7 and afilling machine 21 which is connected to the product pipe 7 andcomprises three filling stations 8. The filling process at each fillingstation 8 is controlled by means of a filling valve 9, a filling pipe 22extending from each filling valve 9.

It will be appreciated that additional filling machines 21 can beconnected to the product pipe 7 and that each filling station 8 maycomprise more than one filling valve 9.

A liquid product thus flows through the product pipe 7 from the producttank 20 through the inventive device 1 and up to the filling stations 8.

For filling a container 10, the filling pipe 22 of a filling station 8is inserted into the container 10, after which the associated fillingvalve 9 is opened and the product is fed into the container 10.

The pressure drop that then arises in the system 19 is compensated forby the inventive device 1 by free collapsing of its tube portion 2.

As is evident from the Figure, the inventive device 1 is mounted at anangle to a horizontal plane. More specifically, the device 1 is orientedso that its outlet 6 is arranged below its inlet 5. This ensures thatthe tube portion 2 collapses in a manner that promotes discharge of theproduct, which is illustrated in FIGS. 7 a and 7 b.

More specifically, the tube portion 2 will initially collapse inconnection with said inlet 5. The reason for this is that the pressurein the tube portion 2, under the action of gravity, is somewhat higherat the outlet 6 than at the inlet 5. Thus, the tube portion 2 inconnection with said inlet 5 will be more inclined to collapse than isthe tube portion 2 in connection with the outlet 6.

As the pressure drops, the tube portion 2 will thus initially collapsein connection with the inlet 5, after which the collapsed part of thetube portion 2 will move, under continued action of gravity, towards theoutlet 6 during the filling process. The discharge of the product fromthe inventive device will be greater than the supply of the product tothe device from the product pipe, and therefore the collapsed part willgrow as it moves towards the outlet, which is evident from FIG. 7 b. Byangling the device in the manner described above, it is thus ensuredthat the product is continuously pressed out from the inventive device 1during the filling process, which for obvious reasons promotes accuratefilling of containers 10.

According to the present invention, a device 1 for compensating forpressure drop in a product pipe 7 as well as a system 19 comprising sucha device 1 are provided.

The device 1 comprises a collapsible tube portion 2 which is connectibleto the product pipe 7. The device 1 further comprises a limiting means 3which is adapted to counteract stretching of the tube portion 2 in thecircumferential direction and also to allow free collapsing thereof.

Since the device comprises a tube portion 2 which is connectibledirectly to a product pipe 7, a device 1 is provided, which is extremelyeasy to clean and sterilise.

The free collapsibility of the tube portion 2 also ensures that apressure drop in the product pipe 7 can effectively be compensated for.

Finally, the capability of the limiting means 3 of counteractingstretching of the tube portion 2 means that the risk of fatigue anddamage owing to repeated stretching of the tube portion 2 is eliminated.This guarantees a satisfactory service life of the inventive device 1.

It will be appreciated that the present invention is not restricted tothe embodiments illustrated.

Several modifications and variations are thus feasible, and thereforethe present invention is exclusively defined by the appended claims.

1. A device (1) for compensating for pressure drop in a product pipe (7)through which a liquid flows, comprising a collapsible tube portion (2)which is connectible to said product pipe (7), wherein a limiting means(3), which is inelastic in the circumferential direction and is adaptedto counteract stretching of the tube portion (2) in the circumferentialdirection, and which is flexible such that it is collapsible freelytogether with the tube portion (2) said device further comprising acasing (4), in which said tube portion (2) and said limiting means (3)are arranged, pressure means (15) arranged to apply a pressureprevailing in the casing (4), which is slightly below a normal pressureprevailing in the tube portion (2) in operation.
 2. A device as claimedin claim 1, wherein the limiting means (3) is integrated into a tubewall (14) of the tube portion (2).
 3. A device as claimed in claim 2,wherein the limiting means (3) comprises a reinforcement (13) integratedinto said tube wall (14).
 4. A device as claimed in claim 1, wherein thelimiting means (3) is arranged outside the tube portion (2).
 5. A deviceas claimed in claim 1, wherein the limiting means (3) has such a tensilestrength as to prevent stretching of the tube portion (2) in thecircumferential direction at a pressure above atmospheric prevailing inthe same in the range of 1–10 bar.
 6. A device as claimed in claim 1,wherein the pressure means (15) is a compressed air means (15).
 7. Adevice as claimed in claim 1, wherein the tube portion (2) is flexibleand stretchable.